Heredity and Evolution — Science STD 10 — Question

Draw a labelled diagram to show the domestic electric wiring from an electric pole to a room. Give the wiring for a bulb and a three-pin socket only.

(i) Name the metal which does not stick to glass?
(ii) Name the non-metal which is a good conductor of electricity?
(iii) Name the metal which is commonly used in thermit welding?
(iv) What gets deposited at the cathode, a pure or impure metal?
(v) What is the nature of Zinc oxide?

Identify the acid and the base from which sodium chloride is obtained. Which type of salt is it? When is it called rock salt? How is rock salt formed?

1. Name a metal for each case:

1. It does not react with cold as well as hot water but reacts with steam.
2. It does not react with any physical state of water?

2. When calcium metal is added to water, the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?

"Natural selection and speciation leads to evolution." Justify this statement.

Why is chemical communication better than electrical impulses as a means of communication between cells in a multi-cellular organism?

Explain with the help of an example each, how the following provide evidences in favour of evolution:

1. Homologous organs.
2. Analogous organs.
3. Fossils.

Why is the colour of the clear sky blue?